The Bicentennial Conservatory is intriguing not simply for what one sees in it, but through it. Passing by a set of renovated Edwardian buildings at the entrance to Adelaide’s Botanic Gardens on the Princes Highway, the city block turns quickly to gardens and bushland.

Beyond, 100m white arch of trussed steel rises and falls, almost covering the entire length of the Rose Garden that neighbours the street.

This is the largest single span conservatory in the Southern Hemisphere. It is clad almost entirely in toughened glass that shelters the subtropical garden within, and perfectly frames the Australian Garden behind it.

The facade possesses two entirely distinct personalities. In approaching through the Botanic Garden’s entry, a sinuous glass sculpture is first encountered, ‘Cascade’ by Sergio Redegalli, rising out of the pond that serves as its podium.

Following its trajectory as it steps upwards, one is led to the foot of the conservatory whose ridge continues skyward.

This face is pyramidal, solid, and white. A seam of glazing at the arch’s ridge opens up to the public at ground level: the entry point into the subtropical greenhouse.

The work of architect Guy Maron in preparation for Australia’s Bicentenary commemoration, the Conservatory was designed to house endangered Australasian tropical flora.

It is a forward-looking extension to the pre-existing horticultural architecture of the garden, preceded by the ornate Victorian Palm House by German architect Gustav Runge in 1875.

As of 2014, it has already joined its predecessor on the South Australian Heritage Register as an excellent example of late-twentieth century Structuralism. This is only twenty-seven years following its construction.

The same red bricks that line the paths of the garden’s walkways follow through the Conservatory.

Just beyond the foyer at the base of the long span arch, these bricks begin to meander through the now subtropical landscape, weaving outwards as the building widens under the 27m apex of the glass roof. Elevated above the brick footpath, a sinuous blue boardwalk winds its way towards the canopy.

The organic quality of the landscape design in the conservatory and its pathways allows the steel superstructure to recede, serving to frame the sky and surrounding Australian Garden canopy beyond its walls.

Beyond the greenhouse effect that operates to heat the interior, a tropical environment has historically been maintained through a humidification system of almost a thousand misting nozzles that run across the roof as well as a heating system.

Yet the Conservatory’s operating costs and energy emissions have been reconsidered by the Board of the Garden in recent years.

Estimated to contribute to over half the Botanic Garden’s emissions, and expensive to maintain, the heating was turned off in 2012.

The structure had ironically performed its job slightly too well; the 25-year old ecosystem had established a robust canopy, limiting light to the ground level that in turn limited further plant growth in its prime exhibition zone.

In opening it up to light, and shifting its focus to subtropical plant species to respond to the new microclimate, the new direction for the Conservatory strengthens its integrity as an ideal precedent for climate responsive and energy efficient architecture.

The greenhouse occupies an aspirational space at the heart modern architecture. It ties fundamental aspects in the evolution of the profession down to two elements; metal and glass, nature and light.

They possess a dramatic quality, tied to their checkered history, overshadowed by their omen, the ashes of the burnt Crystal Palace, London.

Australia champions its own natural sanctuary in Adelaide’s Botanical Garden; The Bicentennial Conservatory.

For more information, go to https://www.architecture.org.au/

Tone Wheeler

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